Linear electrodynamic system and method

ABSTRACT

An exemplary description provided for patent searches includes a linear electrodynamic system for conversion of mechanical motion into electrical power or conversion of electrical power into mechanical motion involving advantageous use of magnetic material positioned on a mover. Bore surfaces of the magnetic material is shape complementary to bore surfaces of stator poles. Some implementations utilize non-annularly shaped bore surfaces while others utilize annularly shaped bore surfaces.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed generally to electrodynamic systemsand, more particularly, to linear alternators and linear motors.

2. Description of the Related Art

Linear electrodynamic systems including linear alternators and linearmotors are particularly useful, for instance, in combination withStirling cycle engines for electrical power generation and forrefrigeration applications. These electrodynamic systems requiresubstantial mass in their construction for adequate performance.Typically, iron laminations are used for the mover and stator componentsand copper wire is used for the windings.

Unfortunately, the amount of mass involved with these linearelectrodynamic systems can be undesirable, for example, with situationswhere construction or operational costs are dependent upon equipmentweight. As another example, for portable equipment, the amount of massused for these linear electrodynamic systems can lessen the ease of useof the equipment.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic drawing of a conventional electrothermal system.

FIG. 2 is a cross-sectional view of the conventional linearelectrodynamic system of FIG. 1 with its mover in a first position.

FIG. 3 is a top view of the conventional stator lamination and aconventional mover lamination pair associated with the mover in thefirst position of FIG. 2.

FIG. 4 is a cross-sectional view of the conventional linearelectrodynamic system of FIG. 1 with its mover in a second position.

FIG. 5 is a top view of the conventional stator lamination and theconventional mover lamination pair associated with the mover in thesecond position of FIG. 4.

FIG. 6 is an exploded isometric view of an implementation of theinnovative linear electrodynamic system according to the presentinvention.

FIG. 7 is an isometric view of the implementation of the linearelectrodynamic system of FIG. 6 showing the mover in a first position.

FIG. 8 is a cross-sectional isometric view taken substantially along theline 8-8 of FIG. 7.

FIG. 9 is an end view of a non-annular convex eight-V implementation ofa stator lamination and a mover lamination pair of the linearelectrodynamic system of FIG. 6 without windings.

FIG. 10 is an end view of a non-annular concave four-parabolicimplementation of a stator lamination and a mover lamination pair of thelinear electrodynamic system according to a second embodiment of thepresent invention.

FIG. 11 is an end view of a non-annular concave four-V implementation ofa stator lamination and a mover lamination pair of the linearelectrodynamic system according to a third embodiment of the presentinvention.

FIG. 12 is an end view of a non-annular convex four-arc implementationof a stator lamination and a mover lamination pair of the linearelectrodynamic system according to a fourth embodiment of the presentinvention.

FIG. 13 is an end view of a non-annular convex four-arc implementationof a stator lamination and a mover lamination pair of the linearelectrodynamic system according to the fifth embodiment of the presentinvention.

FIG. 14 is an end view of a non-annular convex four-V implementation ofa stator lamination and a mover lamination pair of the linearelectrodynamic system according to a sixth embodiment of the presentinvention.

FIG. 15 is an end view of a non-annular convex eight-parabolicimplementation of a stator lamination and a mover lamination pair of thelinear electrodynamic system according to the seventh embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As will be discussed in greater detail herein, an innovative linearelectrodynamic system and method is disclosed to convert linearmechanical motion into an electrical current such as for a linearalternator for heat engines including Stirling cycle engines, or toconvert electrical current into linear mechanical motion such as for alinear motor associated with mechanical cooling devices. Due toinnovative concepts embodied therein and described below, the innovativelinear electrodynamic system has size and weight advantages overconventional linear electrodynamic systems.

A conventional electrothermal system 10 using a heat module 12 and apower module 14 is shown in FIG. 1. When in the form of a Stirling cycleengine, the heat module 12 has a displacer 16 and working fluid 18 influid communication with a power piston 20, which is part of the powermodule 14. The power piston 20 of the power module 14 is connected to aconventional linear electrodynamic system 22 through a shaft 23 coupledto a mover 24. The conventional linear electrodynamic system 22 furtherincludes a stator 26 and a paired electrical line 28 to furnish orreceive electrical power. The stator 26 has conventional statorlaminations 30 stacked together and secured by stator connecting rods 32positioned through stator connecting rod holes 33, as shown in FIG. 2 inwhich the mover 24 is in a first position.

The conventional stator laminations 30 each have four stator polelaminations 34 shown in FIG. 3 in the 3:00, 6:00, 9:00, and 12:00o'clock positions. The stator pole laminations 34 form stator poles 34′of the stator 26 when the stator pole laminations are stacked. Thestator poles 34′ are made of a magnetic field enhancing material, suchas iron, shaped to form slots 35 (best shown in FIG. 3), which receivewindings 36, such as formed by winding copper wire through the statorslots around the stator poles. Orientation of the windings 36 is shownfor a first winding 36 a and a second winding 36 b in FIGS. 2 and 3 andis additionally shown for a third winding 36 c and a fourth winding 36 din FIG. 3.

Four annular concave arc magnets 38 are each glued to a portion (sevenconventional stator laminations 30 in FIG. 2) of one of the four statorpoles 34′ (for instance, the stator pole in the 12:00 position of FIG.3). The annular concave arc magnet 38 is so named because its boresurface 38′ opposite the stator pole 34′ has a concave shape in the formof an arc being in cylindrical alignment with the other annular concavearc magnets attached to the other stator poles of the stator 26. Thiscylindrical alignment of the bore surfaces 38′ of the annular concavearc magnets 38 is depicted by an illustrative circle 39 that is not partof the structure of the stator 26, but is shown in FIGS. 3 and 5 onlyfor explanatory purposes.

The mover 24 is made up of collections of stacked conventional moverlaminations 40 made of a magnetic field enhancing material, such asiron, and has mover sections 41 with arcuate bore surfaces 41′ shaped tocomplement the shape of the bore surfaces 38′ of the annular concave arcmagnets 38.

The annular nature of the annular concave arc magnets 38 allows for themover 24 to be shaped to fit inside the illustrative circle 39 with agaseous gap 43 of typically one-hundredth of an inch between boresurfaces 41′ of the mover sections 41 and the bore surfaces 38′ of theannular concave arc magnets 38. With such an arrangement the rotationaltolerances for securing the mover 24 in the conventional linearelectrodynamic system 22 are not rigorous regarding the amount ofrotation allowed for the mover. Since the bore surfaces 38′ of theannular concave arc magnets 38 are cylindrical coincident with theillustrative circle 39, the arcuate bore surface 41′ of the moversections 41 allow the mover 24 to rotate a significant amount withoutcontacting the stator 26 should torque on the shaft 23 cause the moverto rotate.

The conventional mover laminations 40 are held together by moverconnecting rods 42 inserted through mover connecting rod holes 44. Aportion of the shaft 23 is coupled to the mover 24 through shaft holes45 in the conventional mover laminations 40.

The annular concave arc magnets 38 have a first orientation 38 a inwhich the north pole of the magnet is the bore surface 38′ and a secondorientation 38 b in which the south pole of the magnet is the boresurface. The first orientation 38 a and the second orientation 38 b arealternated along the axis of the shaft 23 as shown in FIG. 2 andalternated around the 3:00, 6:00, 9:00, and 12:00 positions as shown inFIG. 3. Magnetic flux lines 50 are shown in FIG. 3 for a pair of one ofthe conventional stator laminations 30 and an adjacent one of theconventional mover laminations 40 when the mover 24 is in the firstposition shown in FIG. 2. Magnetic flux lines 51 are shown in FIG. 5 forthe pair of one of the conventional stator laminations 30 and anadjacent one of the conventional mover laminations 40 when the mover 24is in a second position shown in FIG. 4.

An innovative linear electrodynamic system 100 is shown in FIG. 6 havingan innovative stator 102, an innovative mover 104, and a shaft 106.Various implementations of the innovative stator 102 and the innovativemover 104 are described below, which result in reduced mass of theinnovative linear electrodynamic system 100 compared with theconventional linear electrodynamic system 22 of comparable performancecapability. Mass reduction is achieved by enhancing magnetic fluxdistribution through the innovative stator 102 and the innovative mover104, reduction of size and volume of the innovative stator and theinnovative mover, and reduction of the amount of metal (typicallycopper) required in the associated windings. Furthermore, as shown inthe implementations below, the innovative stator 102 and the innovativemover 104 are more efficiently packaged to better use available spacecompared with conventional approaches resulting in further reductions ofsize of the innovative linear electrodynamic system 100.

As part of the approach used, the flux is concentrated flux byincreasing total magnet volume found in the innovative linearelectrodynamic system 100. With increases of magnet volume and fluxconcentration, the number of turns in stator windings required todevelop a given voltage is reduced. Increased magnetic flux allows fordecreases in outer diameter of the innovative stator 102 and more narrowpoles of the innovative stator allow for smaller sized turns for statorwindings. Stator mass and volume both scale with the square of statordiameter. As further discussed below, magnets are positioned on theinnovative mover 104 thus generally allowing a comparable shortening ofthe length of the innovative stator 102 by approximately half since theinnovative mover is generally allowed a comparable doubling in length toallow for alternating of magnetic poles. These attributes mentioned canall factor into a significant overall reduction of mass and volumeassociated with the innovative linear electrodynamic system 100 comparedto the conventional linear electrodynamic system 22 of comparableperformance capability.

Shapes of the magnets discussed below found with the innovative linearelectrodynamic system 100 also can reduce magnetic side loading on theinnovative mover 104 as compared with the conventional linearelectrodynamic system 22 described above.

The innovative stator 102 has stator laminations 108, which are stackedtogether using stator connecting rods 109. The innovative stator 102further has windings 110. The non-annular magnets 111 are glued toportions of the innovative mover 104. In the depicted implementations ofthe innovative mover 104 discussed herein, the non-annular magnets 111are arranged on the innovative mover to have first and secondorientations similar to that discussed above for the conventional statorlaminations 30. For instance, with the implementation depicted in FIG. 6in which the magnets' north surfaces 111 n and the magnets' southsurface 111 s are alternated as bore surfaces 111′ of the innovativemover. The non-annular magnets 111 are designated as such because theirnorth bore surfaces 111 n and their south bore surfaces 111 s are not ina cylindrical arrangement such as is the arrangement depicted by theillustrative circle 39 accompanying the description above of theconventional linear electrodynamic system 22.

Being non-annular in nature is a significant departure from conventionalapproaches and not suggested thereby. For instance, use of non-annularmagnets 111 having the north bore surface 111 n and the south boresurface 111 s with a non-annular shape requires that rotationaltolerances for the innovative mover 104 be much more strict thanconventional approaches since even slight rotational movement willresult in the innovative mover 104 striking the innovative stator 102.In addition, the non-annular magnets 111 are so shaped that they canintroduce an additional torque load on the innovative mover 104 thatneed not be addressed by conventional approaches. Conventional linearelectrodynamic systems are designed to avoid these results.

In the first implementation of the present invention shown in FIG. 6,there are eight non-annular stator poles 112 shaped as non-annularconvex V stator poles with bore surfaces 112′. For the implementationshown in FIG. 6, thirty two non-annular magnets 111 are affixed, such asby gluing, to eight mover sections 116 to form eight concave V magnetsections 120. The term “V’ is used due to the general “V” shape of the Vmagnet sections 120 formed from the non-annular magnets 111 in thisimplementation.

The innovative mover 104 is made up of mover laminations 118 which arebound together and define a plurality of the non-annular mover sections116. FIGS. 7 and 8 shows the eight non-annular concave V magnet sections120 of the particular implementation shown in FIGS. 6 of the innovativemover 104 midway in its reciprocal travel within the innovative linearelectrodynamic system 100.

The implementation of FIGS. 6-8 is shown in FIG. 9 from the end withoutthe windings 110 illustrated. There is a gaseous gap 122 between thebore surfaces 111′ of the eight non-annular magnets 111 shown and thecorresponding bore surfaces 112′ of the eight non-annular stator poles112 of the innovative stator 102. Due to the geometry, the design of theinnovative linear electrodynamic system 100 allows little tolerance forrotational movement of the innovative mover 104 relative to theinnovative stator 102. Movement of more than the size of the gaseous gap122 will result in the innovative mover 104 contacting the innovativestator 102. Thus, the innovative mover 104 must be retained with minimalrotational movement as the innovative mover reciprocates longitudinallywithin the innovative stator 102.

The mover laminations 118 each further has a central shaft hole 123 forcoupling the mover lamination to the shaft 106. The innovative stator102 has stator connecting rod holes 124 to receive the stator connectingrods 109. The innovative stator 102 further has stator slots 125positioned between the non-annular stator poles 112 and shaped toaccommodate the windings 110 with each extending above one of thenon-annular stator poles 112 and shaped to accommodate the shape andpositioning of the innovative mover 104. Connector rod holes (not shown)are provided in the mover laminations 118 for securing the moverlaminations 118 of the innovative mover 104 together with connectingrods.

A second implementation of the innovative stator 102 and the innovativemover 104 is shown in FIG. 10. In this implementation, the innovativestator 102 has four non-annular concave parabolic stator poles 126 withstator pole voids 127. The stator pole voids 127 are formed to reducethe mass of the non-annular concave parabolic stator poles 126. Twonon-annular convex parabolic magnets 128 with bore surfaces of oppositepolarity are coupled to a different one of four mover sections 130. Thenon-annular convex parabolic magnets 128 are so named because in thisimplementation the bore surfaces 128′ of the non-annular magnets 128have a convex parabolic shape and are non-annular in terms of the abovediscussion regarding the illustrative circle 39.

The innovative mover 104 of the implementation of FIG. 10 has the fourmover sections 130 complementary to the four non-annular concaveparabolic stator poles 126 such that only the gaseous gap 122 existsbetween the stator poles 126 and the bore surfaces of the fournon-annular convex parabolic magnets 128. The mover sections 130 havemover section voids 131 to reduce the mass of the innovative mover 104and to receive connecting rods (not shown) to hold the mover laminationstogether.

A third implementation of the innovative stator 102 and the innovativemover 104 is shown in FIG. 11. In this implementation, the innovativestator 102 has four non-annular concave V stator poles 132 with statorpole voids 133. The stator pole voids 133 are formed to reduce the massof the non-annular concave V stator poles 132. Two non-annular convex Vmagnets 134 with bore surfaces of opposite polarity are coupled to adifferent one of four mover sections 136. The non-annular convex Vmagnets 134 are so named because in this implementation the boresurfaces of the non-annular magnets 134 have a convex V shape and arenon-annular in terms of the above discussion regarding the illustrativecircle 39.

The innovative mover 104 of the implementation of FIG. 11 has the fourmover sections 136 complementary to the four non-annular concave Vstator poles 132 such that only the gaseous gap 122 exists between thestator poles 126 and the bore surfaces of the four non-annular convex Vmagnets 134. The mover sections 136 have mover section voids 137 toreduce the mass of the innovative mover 104 and to receive connectingrods (not shown) to hold the mover laminations together.

A fourth implementation of the innovative stator 102 and the innovativemover 104 is shown in FIG. 12. In this implementation, the innovativestator 102 has four non-annular convex arc stator poles 138 with statorpole voids 139. The stator pole voids 139 are formed to reduce the massof the non-annular convex arc stator poles 138. Two non-annular concavearc magnets 140 with bore surfaces of opposite polarity are coupled to adifferent one of four mover sections 142. The non-annular concave arcmagnets 140 are so named because in this implementation the boresurfaces of the non-annular magnets 140 have a concave arc shape and arenon-annular in terms of the above discussion regarding the illustrativecircle 39.

The innovative mover 104 of the implementation of FIG. 12 has the fourmover sections 142 complementary to the four non-annular convex arcstator poles 138 such that only the gaseous gap 122 exists between thestator poles 138 and the bore surfaces of the four non-annular concavearc magnets 140. The mover sections 142 have mover section voids 143 toreduce the mass of the innovative mover 104 and to receive connectingrods (not shown) to hold the mover laminations together.

A fifth implementation of the innovative stator 102 and the innovativemover 104 is shown in FIG. 13. In this implementation, the innovativestator 102 has four non-annular convex parabolic stator poles 144 withstator pole voids 145. The stator pole voids 145 are formed to reducethe mass of the non-annular convex parabolic stator poles 144. Twonon-annular concave parabolic magnets 146 with bore surfaces of oppositepolarity are coupled to a different one of four mover sections 148. Thenon-annular concave parabolic magnets 146 are so named because in thisimplementation the bore surfaces of the non-annular magnets 146 have aconcave parabolic shape and are non-annular in terms of the abovediscussion regarding the illustrative circle 39.

The innovative mover 104 of the implementation of FIG. 13 has the fourmover sections 148 complementary to the four non-annular convexparabolic stator poles 144 such that only the gaseous gap 122 existsbetween the stator poles 144 and the bore surfaces of the fournon-annular concave parabolic magnets 146. The mover sections 148 havemover section voids (not shown) to reduce the mass of the innovativemover 104 and to receive connecting rods (not shown) to hold the moverlaminations together.

A sixth implementation of the innovative stator 102 and the innovativemover 104 is shown in FIG. 14. In this implementation, the innovativestator 102 has four non-annular convex V stator poles 150 with statorpole voids 151. The stator pole voids 151 are formed to reduce the massof the non-annular convex V stator poles 150. Two non-annular concave Vmagnets 152 with bore surfaces of opposite polarity are coupled to adifferent one of four mover sections 154. The non-annular concave Vmagnets 152 are so named because in this implementation the boresurfaces of the non-annular magnets 152 have a concave V shape and arenon-annular in terms of the above discussion regarding the illustrativecircle 39.

The innovative mover 104 of the implementation of FIG. 14 has the fourmover sections 154 complementary to the four non-annular convex V statorpoles 150 such that only the gaseous gap 122 exists between the statorpoles 150 and the bore surfaces of the four non-annular convex V magnets152. The mover sections 154 have mover section voids (not shown) toreduce the mass of the innovative mover 104 and to receive connectingrods (not shown) to hold the mover laminations together.

A seventh implementation of the innovative stator 102 and the innovativemover 104 is shown in FIG. 15. In this implementation, the innovativestator 102 has eight non-annular convex parabolic stator poles 156 withstator pole voids 157. The stator pole voids 157 are formed to reducethe mass of the non-annular convex parabolic stator poles 156. Twonon-annular concave parabolic magnets 158 with bore surfaces of oppositepolarity are coupled to a different one of eight mover sections 160. Thenon-annular concave parabolic magnets 158 are so named because in thisimplementation the bore surfaces 158′ of the non-annular magnets 158have a concave parabolic shape and are non-annular in terms of the abovediscussion regarding the illustrative circle 39.

The innovative mover 104 of the implementation of FIG. 15 has the eightmover sections 160 complementary to the eight non-annular convexparabolic stator poles 156 such that only the gaseous gap 122 existsbetween the stator poles 156 and the bore surfaces of the eightnon-annular concave parabolic magnets 158. The mover sections 160 havemover section voids 161 to reduce the mass of the innovative mover 104and to receive connecting rods (not shown) to hold the mover laminationstogether.

In some of the implementations shown, the number of non-annular statorpoles for the innovative stator 102 was eight rather than four. Otherimplementations are possible including six, eight, ten, and other evennumbers of non-annular stator poles. As shown in FIGS. 1-5, conventionalapproaches have used four stator poles 34′ for the stator 26 of theconventional linear electrodynamic system 22. Increasing the number ofnon-annular stator poles as with some implementations of the presentinvention can allow further increase in magnet volume and acorresponding reduction in the number of turns generally required forthe windings 110 thereby further reducing total mass and size of theinnovative linear electrodynamic system 100.

Although certain curvilinear and angular shapes, including V shapes andparabolas, for the bore surface of the non-annular magnets are used inthe depicted implementations, other non-annular shapes for the boresurfaces of the non-annular magnets are envisioned for additionalimplementations to increase magnet volume while reducing the size of thenon-annular stator poles for the innovative linear electrodynamic system100 as compared with the annularly oriented conventional linearelectrodynamic system 22. These non-annular shapes can include otheropen curves such as hyperbola, special curves, symmetrically angularshapes, or non-symmetrical or other non-regular curves or angularshapes, in distinction over conventional annular approaches to therebyincrease magnet volume and to decrease the size of the non-annularstator poles for comparable performance capability and an overall massreduction of the innovative linear electrodynamic system 100. Softwaresuch as ANSOFT Maxwell 2D/3D can be used to perform magnetic circuitanalysis to help determine desired curvatures for the non-annularmagnets to be further balanced with other concerns associated withperformance, mass reduction, ease of component manufacture and assembly,and quality control for the innovative linear electrodynamic system 100.These various shapes can be obtained by gluing or otherwise affixingflat pieces of flat magnets to the variously shaped surfaces and/or byforming curves or other shapes into the structure of the magnets.

As discussed above, the non-annular nature of the innovative stator 102and the innovative mover 104 is a significant departure from theconventional approach. Contrary to the conventional approach, there canonly be less than a gaseous gap for the innovative mover 104 to rotatebefore it strikes the innovative stator 102. Because of theextraordinary demand placed upon rotational tolerances for theinnovative mover 104, the innovative linear electrodynamic system 100 isfurther enhanced.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A system comprising: a housing; a longitudinal shaft movably coupledto the housing to longitudinally and linearly reciprocate relative tothe housing in the longitudinal direction of the shaft; a stator rigidlycoupled to the housing, the stator shaped to define an inner space toreceive a portion of the longitudinal shaft, the stator having statorpoles extending inwardly with bore surfaces facing toward that portionof the longitudinal shaft received by the stator; windings wound aroundthe stator poles; a mover affixed to the shaft, the mover; and magneticmaterial affixed to the mover, the magnetic material having boresurfaces facing outward in correspondence with the bore surfaces of thestator poles to define a gaseous gap between each of the correspondinglypositioned ones of the bore surfaces of the magnetic material and thestator poles, portions of the bore surfaces of the stator poles beingcloser to the shaft than portions of the bore surfaces of the magneticmaterial.
 2. The system of claim 1 wherein the bore surface of at leasta portion of the magnetic material affixed to the mover comprises aconcave shape.
 3. The system of claim 2 wherein the bore surface of atleast a portion of the magnetic material affixed to the mover comprisesan arc shape.
 4. The system of claim 1 wherein the bore surface of atleast a portion of the magnetic material affixed to the mover comprisesa V shape.
 5. The system of claim 4 wherein the bore surface of at leasta portion of the magnetic material affixed to the mover comprises aconvex shape.
 6. The system of claim 4 wherein the bore surface of atleast a portion of the magnetic material affixed to the mover comprisesa concave shape.
 7. The system of claim 1 wherein the bore surface of atleast a portion of the magnetic material affixed to the mover comprisesa parabolic shape.
 8. The system of claim 7 wherein the bore surface ofat least a portion of the magnetic material affixed to the movercomprises a convex shape.
 9. The system of claim 7 wherein the boresurface of at least a portion of the magnetic material affixed to themover comprises a concave shape.
 10. A system comprising: a longitudinalshaft mounted for longitudinal and linear reciprocal movement; a statorshaped to define an inner space to receive a portion of the longitudinalshaft, the stator having stator poles extending inwardly with boresurfaces facing toward that portion of the longitudinal shaft receivedby the stator; windings wound around the stator poles; a mover affixedto the shaft; and magnetic material affixed to the mover, the magneticmaterial having bore surfaces facing outward in correspondence with thebore surfaces of the stator poles to define a gaseous gap between eachof the correspondingly positioned ones of the bore surfaces of themagnetic material and the stator poles, portions of the bore surfaces ofthe stator poles being substantially the same distance from the shaft asportions of the bore surfaces of the magnetic material.
 11. A systemcomprising: a stator defining an inner space, the stator having statorpoles with bore surfaces extending inwardly within the inner space; amover positioned within the inner space for longitudinal and linearreciprocal movement therein; windings wound around the stator poles; andmagnetic material affixed to the mover and having outwardly facingsurfaces positioned in correspondence with the bore surfaces of thestator poles to define a gaseous gap between each of the correspondinglypositioned ones of the outwardly facing surfaces of the magneticmaterial and the inwardly facing surface portions of the mover, themagnetic material positioned on the mover within the inner space topermit uninhibited longitudinal and linear reciprocal movement of themover within the inner space while limiting rotational movement of themover more than the distance of the gaseous gap existing between thecorrespondingly positioned ones of the inwardly facing bore surfaces ofthe stator and the outwardly facing surface portions of the magneticmaterial.
 12. A system comprising: a stator with inwardly extendingstator poles, the stator defining an inner space with the stator poleshaving bore surfaces defining a portion of the inner space; windingswound around the stator poles; a mover positioned within the inner spacefor longitudinal and linear reciprocal movement therein; and magneticmaterial affixed to the mover, the magnetic material having boresurfaces facing outward in correspondence with the bore surfaces of thestator poles to define a gaseous gap between each of the correspondinglypositioned ones of the bore surfaces of the magnetic material and thebore surfaces of the stator poles, the bore surfaces of the magneticmaterial and the bore surfaces of the stator poles having matingnon-annular shapes.
 13. The system of claim 12 wherein the bore surfaceof each of the stator poles has a convex shape.
 14. The system of claim13 wherein the bore surface of each of the stator poles has an arcshape.
 15. The system of claim 12 wherein the bore surface of each ofone of the stator poles has a V shape.
 16. The system of claim 15wherein the bore surface of each of the stator poles has a concaveshape.
 17. The system of claim 15 wherein the bore surface of each ofthe stator poles has a convex shape.
 18. The system of claim 12 whereinthe bore surface of each of the stator poles has a parabolic shape. 19.The system of claim 18 wherein the bore surface of each of the statorpoles has a concave shape.
 20. The system of claim 18 wherein the boresurface of each of the stator poles has a convex shape.
 21. A methodcomprising: providing a stator with inwardly extending stator poles;shaping the stator to define an inner space, the stator poles havingbore surfaces positioned to extend toward the inner space; winding wirearound the stator poles to form stator pole windings; providing a moverpositioned within the inner space for longitudinal and linear reciprocalmovement therein; affixing magnetic material to the mover, the magneticmaterial having bore surfaces facing outward toward the bore surfaces ofthe stator poles; to define a gaseous gap between each of thecorrespondingly positioned ones of the bore surfaces of the magneticmaterial and the bore surfaces of the stator poles, the bore surfaces ofthe magnetic material having a shape to mate with the bore surfaces ofthe stator poles.
 22. The method of claim 21 wherein the bore surfacesof the magnetic material have non-annular shapes.
 23. The method ofclaim 21 wherein the inner space has a longitudinal axis along which themover longitudinally and linearly reciprocates within the inner space,portions of the bore surfaces of the stator poles being closer to thelongitudinal axis of the inner space than portions of the bore surfacesof the magnetic material.
 24. The method of claim 21 wherein the innerspace has a longitudinal axis along which the mover longitudinally andlinearly reciprocates within the inner space, portions of the boresurfaces of the stator poles being substantially the same distance fromthe longitudinal axis of the inner space as portions of the boresurfaces of the magnetic material.
 25. The method of claim 21 whereinthe magnetic material is positioned on the mover to permit uninhibitedlongitudinal and linear reciprocal movement of the mover within theinner space while being positioned on the mover such that rotationalmovement of the mover is limited to no more than the distance of thegaseous gap existing between the correspondingly positioned ones of theinwardly facing bore surfaces of the stator poles and the outwardlyfacing bore surfaces of the magnetic material.